U.S. Pat. No. 5,532,593 to Maneval et al. discloses an apparatus and method for obtaining rheological information about a fluid using nuclear magnetic resonance. A fluid flowing through a tube is subjected to nuclear magnetic resonance imaging signals to obtain the velocity profile of the fluid. The pressure gradient between two points along the tube is also obtained. The shear rate is then determined from the velocity profile, and the shear stress is determined from the pressure gradient. From a single velocity profile, data is obtained over shear rates ranging from zero at the center of the tube to the maximum shear rate at the tube wall. Alternatively, the velocity spectrum can be obtained and used in the same manner. The shear stress versus shear rate curve can thereby be obtained from a single nuclear magnetic resonance image taken at a specific value of the pressure gradient. However, only a radial (2D) velocity profile is taught in U.S. Pat. No. 5,532,593.
U.S. Pat. No. 5,757,187 to Wollin discloses a device and a method wherein weak oscillating gradients are used to modulate the angular momentum of the spins in a magnetic resonance imaging apparatus producing output signals in the receiver coil which can be synchronously demodulated to yield a periodic envelope containing integral harmonics of the oscillating gradient frequency. This periodic envelope is subjected to synchronous detection, continuously yielding the amplitudes of the individual harmonic components of the envelope which are then used to approximate an integral equation by a matrix solution to a linear transformation which generates the Radon transform of the transverse magnetization along the direction of the oscillating gradient, permitting image reconstruction. Truncation (Gibbs) artefacts are eliminated. Synchronous demodulation and synchronous detection of the impulse spectrum of the output signal from the receiver coil suppresses the continuous spectrum Johnson noise. The very weak higher harmonics are synchronously detected over multiple periods yielding an improved estimate of their central tendency. However, Wollin teaches a method of measuring a radial (2D) velocity profile and Wollin does not teach a method of deriving rheological parameters from the velocity data.
It is therefore a long felt need to provide a system and method for obtaining rheological information about a flowing fluid that is not limited to radial (2D) measurements.